Is this the world's oldest bike?

I saw this machine at a Leonardo Da Vinci exhibition in Brisbane earlier today (although this particular picture was nicked from a random flickr account). Apparently Leonardo Da Vinci came up with this design sometime around 1493, although it was probably never built because, being 400 years ahead of it's time (like most of Da Vinci's designs), it was probably greeted with a lot of "that will never work" critiques.
There are some suggestions flying around on the Internet that this may be a hoax. Still, I have to confess that I was wondering how it would ride up Mt Nimmel when I saw it.
My ride up Mt Nimmel in the moonlight on Wednesday was the best I've had since my crash last week. I've been feeling my way back just to make sure my knee is 100%, and it seems to be close after it coped with Mt Nimmel. In the meantime, I've been turning my attetion to other things as, much to my chagrin, I can't go and ride 250km each day. Last night I went to a free concert in Brisbane from local band The Boat People. Those who remember when I used to make the occasional music post on this blog would be aware of them, those who aren't should click on the link and take a listen. They put on a great live show, these guys are the real deal.